LoPresti Speed Spat Product and Performance Report
Arrow-II PA-28R-200
May 30, 2009
 Before getting into the report, let me say that I am not
affiliated with LoPresti. My comments and findings are based on
the installation of a set of LoPresti SpeedMerchants
SpeedSpats
(main landing gear fairings) on my personal aircraft, a 1974
Arrow-II. There is nothing special about this Arrow. For those
who want to compare performance figures to their own Arrow, mine
has a high-time engine and it has a 3-blade Hartzell propeller.
Why LoPresti Speed Spats? The answer arrived from a number of
reasons that fit me (but perhaps will not fit others). First,
the Arrow fits our family lifestyle the best and I have no
interest in purchasing another aircraft with faster inherent
speed at this time. That being said, I wanted a little faster
cruise performance – and that pointed me in the direction of
speed modifications for the Arrow. LoPresti happens to be
located at my airport home base of Sebastian, FL (they just
relocated from Vero Beach) – which caused me to favor their
products versus others on the market. Of all the LoPresti speed
mod products for the Arrow-II, the Speed Spats and the new
engine cowling promised (according to LoPresti’s literature) the
greatest speed gains. And since the cost of the cowling is more
than my pocketbook can handle, I focused on the Speed Spats.
The LoPresti Speed Spats come as a kit with four (4) molded
fiberglass parts with a white gel-coat type product coating on
the outside; and bare fiberglass on the inside. The kit comes
with a tube of special adhesive; one pair of Latex gloves; an
ample supply of pull-rivets; a 0.125” drill bit; installation
instructions; STC information; and set of master drawings.
This photo shows the fairing part that is attached to the
underside of the flap
Installation is straightforward and easily accomplished by
anyone that knows how to hold a cordless drill. Note: this
installation is considered a major alteration and as such the
work needs to be conducted by or under the supervision of an
A&P. Ultimately a Form 337 is needed to complete the required
FAA paperwork; and it must be signed by an IA.
This photo shows the installation of the part that partially
fits inside the wheel well. Cleco’s are used to hold the part in
place while pull-rivets are installed. Masking tape outlines the
part to protect the surrounding area from the adhesive. The flap
actuator has been removed so the flap can be dropped to make it
easier to install the pull-rivets.
The installation requires some cutting and sanding of the
parts to make them fit. Cutting is accomplished with a simple
band saw or hack saw. Sanding is done with 12” long block of
wood and sand paper.
After the parts are fitted, holes are drilled to receive the
rivets. The parts are temporarily held in place with 1/8” Cleco
fasteners. The surfaces of the aircraft where the parts will be
bonded are cleaned with Alcohol to allow the adhesive to bond
properly. The two-part adhesive/sealer comes in a handy
container that allows mixing the components inside the original
packaging. The adhesive is then spread onto the fiberglass parts
where they come in contact with the aircraft. Position the parts
using Cleco’s; and then begin installing the 80-something rivets
that secure the completed parts.
Aircraft on jacks with LoPresti Speed Spats installed
Profile view of LoPresti Speed Spats installed
Note the LoPresti “Hubba
Hubba” Hub Caps (a gift from my son last Christmas)
The Hubba Hubba Hub Caps have a curvature that adds to the
aerodynamics of the Speed Spat installation
It took about 8-manhours to do the work (including 1-hour of
head scratching). I did all the work with an A&P/IA supervising.
A licensed LoPresti installation shop would certainly do the job
in less time.
How Do They Work? Actually, they do well! After
hearing several reports that speed mods in general are not worth
the cost or effort – I was anxious to learn if the LoPresti
SpeedSpats offered measurable performance improvements.
Before installing the SpeedSpats I flew the aircraft at various
altitudes and power settings to establish a base line of
performance numbers. After the installation I flew the same
flight profile and recorded the numbers.
1974 Arrow II
PA28R-200 Arrow-II with 3-blade propeller
LoPresti Speed Spats (main landing gear fairings)
Performance Comparison Without-With Speed Spats
*Please note that LoPresti claims 4 mph at 75%
power at 7500 feet.
The Data
| |
Prior to and after SpeedSpat Installation |
|
|
|
|
|
Before MPH |
Before TAS MPH |
After MPH |
After TAS MPH |
Delta |
% gain |
|
A |
144 |
155 |
146 |
157 |
2 |
1.3% |
|
B |
137 |
147 |
139 |
149 |
2 |
1.4% |
|
C |
135 |
145 |
138 |
148 |
3 |
2.1% |
|
D |
146 |
162 |
150 |
166 |
4 |
2.5% |
|
E |
134 |
149 |
137 |
152 |
3 |
2.0% |
|
F |
135 |
155 |
139 |
160 |
5 |
3.2% |
| |
|
|
|
|
|
|
|
|
OAT |
Alt |
MAP |
RPM |
GPH |
% Power |
|
A |
20 |
3500 |
24.5 |
2400 |
10.2 |
75% |
|
B |
20 |
3500 |
22.1 |
2400 |
9.2 |
65% |
|
C |
20 |
3500 |
24.9 |
2100 |
9.2 |
65% |
|
D |
16 |
5500 |
24.8 |
2400 |
10.2 |
75% |
|
E |
16 |
5500 |
21.6 |
2400 |
9.2 |
65% |
|
F |
15 |
7500 |
21.6 |
2400 |
9.2 |
65% |
Hope this information is helpful to those who are thinking of
adding speed mods to their Arrow.
Scott B
Sebastian, FL
More info
|
